A washing machine is an apparatus that can remove contaminants from laundry such as clothes through a process of washing the laundry.
The washing machine may be classified into a top loading type washing machine in which the axis of rotation of a drum is perpendicular to the ground, and a front loading type washing machine in which the axis of rotation of a drum is parallel to the ground.
In the top loading type washing machine where the axis of rotation of the drum is substantially perpendicular to the ground, the drum may be provided in a tub that can store wash water, and washing may be performed in a pulsator mode where laundry is washed in a state in which the laundry is immersed in wash water supplied into the drum.
In the pulsator mode, washing may be performed by friction between wash water and laundry and by action of detergent through the rotation of the drum or the rotation of a pulsator that is provided in the lower part of the drum to generate a stream of water. In the pulsator mode, however, washing may be performed only when the wash water is supplied such that the laundry is immersed in the wash water. As a result, a large amount of wash water may be used for washing.
In the front loading type washing machine where the axis of rotation of the drum is substantially parallel to the ground, washing may be performed in a drum washing mode, in which washing is performed by friction between the drum that is rotated by driving force from a motor and laundry and by dropping movement of the laundry in a state in which detergent, wash water, and the laundry are received in the drum.
In the drum washing mode, the laundry may be little damaged, may not become tangled, and may be washed in a striking and rubbing fashion.
In a drum washing machine, which performs washing in the drum washing mode, the axis of rotation of the drum is substantially parallel to the ground. As a result, a portion of the drum may be immersed in wash water even when a small amount of wash water is provided in a tub and the drum. Washing may be performed by friction between the drum that is rotated and laundry and by dropping movement of the laundry in the drum.
Although the tub is not driven, when the drum is rotated at a high speed, wash water may be distributed not only to the lower part of the tub but also to an inner circumferential surface of the tub. In some cases, contaminants or scales may accumulate on the entirety of the inner circumferential surface of the tub. For example, once contaminants or scales accumulate on the inside surface of a door or the upper part of the inner circumferential surface of the tub and are dried, it may be not easy to remove the contaminants or scales therefrom since they are not immersed in wash water.
In some examples of a conventional drum washing mode, a predetermined amount of wash water may be supplied into the tub, and the drum may be accelerated to a specific rotational speed such that the wash water cleans the inner circumferential surface of the tub while it circulates along the inner circumferential surface of the tub according to the rotation of the drum.
In some cases of the conventional drum washing mode, if an eccentric amount of the drum exceeds a reference eccentric amount at a step of accelerating the drum to a specific rotational speed, the drum is decelerated to 0 RPM or a very low rotation speed, and then a subsequent cycle is performed. That is, if the eccentric amount of the drum exceeds a reference eccentric amount at the acceleration step for cleaning the tub, the cleaning of the tub may be skipped. As a result, a success rate of tub cleaning is reduced.
In the conventional drum washing mode, the drum may be rotated at a high speed with water that is suppled after laundry is removed from the drum. Because the supplied water is discharged without being used in a subsequent step, the water may be wasted.
In some examples, detergent may be used for tub cleaning. The detergent for tub cleaning may contain a large amount of chemical components that may cause water pollution. Although the detergent for tub cleaning may have powerful washing force than detergent for washing laundry, it may not be environmentally friendly.